Laterally Excited Bulk Wave Structure for Heat and Power Durability

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Solution Overview

Problem

Existing bulk acoustic wave devices face challenges in achieving high frequency resonance and power durability while maintaining effective heat dissipation and mechanical ruggedness, particularly in 5G NR applications where higher transmit powers are required.

Innovation Solution

A laterally excited bulk acoustic wave device is designed with a piezoelectric layer between solid acoustic mirrors on a support substrate, which includes an interdigital transducer electrode to laterally excite bulk acoustic waves and confine acoustic energy, and a second substrate for heat dissipation, improving mechanical ruggedness and thermal conductivity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If bulk acoustic wave devices use higher transmit powers for 5G NR applications, then power durability is improved, but heat dissipation becomes more difficult

Engineering Contradiction:

Improvepower durabilityVSAvoidheat dissipation

Core Design Contradiction:

ReliabilityVSTemperature

Solution Approach 1:

The device is segmented into distinct functional layers: piezoelectric layer for acoustic wave generation, solid acoustic mirrors for energy confinement, and support substrate for heat dissipation. This segmentation allows each component to optimize its specific function, particularly enabling effective heat dissipation through the support substrate while maintaining power durability in the piezoelectric layer.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Solid acoustic mirrors act as intermediary structures between the piezoelectric layer and support substrate. These mirrors confine acoustic energy within the piezoelectric layer while allowing thermal energy to pass through to the support substrate for dissipation, thus mediating between the conflicting requirements of power durability and heat dissipation.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Loss of energy

If solid acoustic mirrors are used to confine acoustic energy, then acoustic energy leakage is reduced, but device complexity increases

Engineering Contradiction:

Improveacoustic energy leakageVSAvoiddevice complexity

Core Design Contradiction:

Loss of energyVSDevice complexity

Solution Approach 1:

The acoustic mirror structure extracts and separates the energy confinement function from the piezoelectric layer itself. By placing dedicated reflective layers at the boundaries, the design simplifies the overall structure while effectively preventing acoustic energy leakage, as the mirrors are positioned only where needed at the interfaces.

Inventive Principle:

Principle #2Taking out (Extraction)

3Strength

If the piezoelectric layer thickness is increased to improve mechanical ruggedness, then mechanical strength is improved, but resonant frequency decreases

Engineering Contradiction:

Improvemechanical ruggednessVSAvoidresonant frequency

Core Design Contradiction:

StrengthVSSpeed

Solution Approach 1:

The device uses asymmetric structure design where the piezoelectric layer thickness is optimized for mechanical strength while solid acoustic mirrors with specific thickness ratios (high impedance layer thickness between 0.14λp to 0.45λp) provide the necessary acoustic confinement. This asymmetric configuration allows the piezoelectric layer to be sufficiently thick for mechanical ruggedness without compromising resonant frequency, as the mirrors compensate for the thickness increase.

Inventive Principle:

Principle #4Asymmetry

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This configuration achieves high frequency resonance, desirable power durability, and efficient heat dissipation, making it suitable for 5G NR applications by reducing acoustic energy leakage and enhancing thermal management.

Implementation Method 1

an interdigital transducer electrode on the piezoelectric layer, and a support substrate arranged to dissipate heat associated with the bulk acoustic wave. The interdigital transducer electrode is arranged to laterally excite a bulk acoustic wave.

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Implementation Method 2

The first solid acoustic mirror and the second solid acoustic mirror are arranged to confine acoustic energy of the bulk acoustic wave.

Methodology Applied

Scientific EffectAcoustic reflection: Reflection

Implementation Method 3

a support substrate arranged to dissipate heat associated with the bulk acoustic wave

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Data Source

PatentUS11552614B2Laterally excited bulk wave device with acoustic mirrors

Publication Date: 2023.01.10 SKYWORKS SOLUTIONS INC

AI summary

A laterally excited bulk acoustic wave device is disclosed. The laterally excited bulk acoustic wave device can include a first solid acoustic mirror, a second solid acoustic mirror, a piezoelectric layer that is positioned between the first solid acoustic mirror and the second solid acoustic mirror, an interdigital transducer electrode on the piezoelectric layer, and a support substrate arranged to dissipate heat associated with the bulk acoustic wave. The interdigital transducer electrode is arranged to laterally excite a bulk acoustic wave. The first solid acoustic mirror and the second solid acoustic mirror are arranged to confine acoustic energy of the bulk acoustic wave. The first solid acoustic mirror is positioned on the support substrate.